Heterologous differentiation has only been previously reported twice in metastatic uterine leiomyosarcomas. We report herein the first case of metastatic uterine leiomyosarcoma with rhabdomyosarcomatous differentiation. A 67-yr-old woman presented with femur, abductor magnus, and lymph node metastases 9 yr after the primary diagnosis. The metastatic sites showed rhabdomyosarcomatous morphologic features, and immunohistochemical studies confirmed skeletal muscle differentiation. Molecular testing revealed the same loss-of-function TP53 mutation in the uterine leiomyosarcoma and metastatic sites supporting heterologous differentiation of the primary tumor. Our case highlights the morphologic shifts metastatic tumors may manifest and the potential diagnostic problems that may arise.

此前仅报道过两次转移性子宫平滑肌肉瘤的异源分化。我们在此报告第一例伴有横纹肌肉瘤分化的转移性子宫平滑肌肉瘤。一名 67 岁女性在初次诊断 9 年后出现股骨、大展肌和淋巴结转移。转移部位显示横纹肌肉瘤形态特征，免疫组织化学研究证实骨骼肌分化。分子测试显示，子宫平滑肌肉瘤和转移部位存在相同的TP53功能丧失突变，支持原发肿瘤的异源分化。我们的病例强调了转移性肿瘤可能表现出的形态变化以及可能出现的潜在诊断问题。